Navratri is a 9-day long Hindu festival celebrated in almost every part of India, typically falling between September and October during the month of Ashvin. The festival is dedicated to the worship of 9 forms of the Goddess Durga, who is also known as the divine Devi. The festival is celebrated with a lot of fanfare and excitement, and each of the nine days is considered very auspicious.
The story associated with Navratri is the battle that occurred between Goddess Durga and the demon Mahishasura. Mahishasura had been granted immortality by Lord Brahma and had been told that he could only be defeated by a woman. He attacked Trilok (Earth, Heaven, and Hell), and the Gods were not able to defeat him. Durga fought the demon for 10 days, and it proved quite difficult as he kept changing his form to confuse the goddess. However, when he finally turned into a buffalo, Durga was able to defeat him.
Each day of Navratri is represented by a different color which symbolizes one of Durgas distinct characteristics or traits. Many Hindus wear a different colored traditional outfit each day to reflect this. The festival ends with whats known as Dussehra, which is the celebration of good over evil.